fix deadlock in condition wait whenever there are multiple waiters

[musl] / src / thread / pthread_cond_signal.c

diff --git a/src/thread/pthread_cond_signal.c b/src/thread/pthread_cond_signal.c
index 574f5c7..e8ed71c 100644 (file)
--- a/src/thread/pthread_cond_signal.c
+++ b/src/thread/pthread_cond_signal.c
@@ -2,7 +2,8 @@
 
 int pthread_cond_signal(pthread_cond_t *c)
 {
-       c->_c_block = 0;
-       __wake(&c->_c_block, 1, 0);
+       int w = c->_c_waiters;
+       if (a_swap(&c->_c_block, 0) || w)
+               __wake(&c->_c_block, 1, 0);
        return 0;
 }